Magnetic head, method of manufacturing magnetic head and information recording apparatus

1. A magnetic head comprising: a pair of magnetic poles disposed to be adjacent to or in contact with a moving recording medium, said pair of magnetic poles being placed adjacent one another with a predetermined interval at an adjacent point or a contact point with respect to the recording medium, in which a magnetic field is generated between the magnetic poles so that the recording medium is magnetized as it moves, a pair of sub-magnetic poles disposed between said pair of magnetic poles; and a pair of non-magnetic films disposed between said pair of sub-magnetic poles, a soft magnetic film extending between said pair of non-magnetic films, and wherein said soft magnetic film has a saturation magnetic flux density not more than a saturation magnetic flux density of one of said pair of magnetic poles located at said lower stream side with respect to a moving direction of said recording medium and also has a saturation magnetic flux density not less than a saturation magnetic flux density of another one of said pair of magnetic poles located at an upper stream side with respect to said moving direction of said recording medium.

2. A magnetic head according to claim 1 , wherein said soft magnetic film has a length with respect to a direction perpendicular to said recording medium, said length being shorter than that of said pair of magnetic poles measured in said perpendicular direction.

3. A magnetic head according to claim 1 , wherein the soft magnetic film has a thickness of 0.075 m or less.

4. A magnetic head according to claim 1 , wherein one of said pair of non-magnetic films is adjacent to a one of said pair of magnetic poles located at a lower stream side with respect to said moving direction of said recording medium, and has a thickness of 0.2 m or less.

5. A magnetic head according to claim 1 , wherein said soft magnetic film has a size smaller than that of a width direction of said pair of magnetic poles with respect to said width direction along said recording medium perpendicular to said moving direction.

6. An information recording apparatus comprising: a magnetic head disposed to be adjacent to or in contact with a moving recording medium while carrying a magnetization on each point of a surface of said recording medium, wherein information is recorded on each point of said recording medium by reversing a direction of the magnetization, said magnetic head further comprising: a pair of magnetic poles placed adjacent one another with a predetermined interval at an adjacent point or a contact point with respect to said recording medium, in which a magnetic field is generated between said pair of magnetic poles so that said recording medium is magnetized as it moves, a pair of sub-magnetic poles disposed between said pair of magnetic poles; and a pair of non-magnetic films disposed between said pair of sub-magnetic poles, a soft magnetic film extending between said pair of non-magnetic films, and wherein said soft magnetic film has a saturation magnetic flux density not more than a saturation magnetic flux density of one of said pair of magnetic poles located at said lower stream side with respect to a moving direction of said recording medium and also has a saturation magnetic flux density not less than a saturation magnetic flux density of another one of said pair of magnetic poles located at an upper stream side with respect to said moving direction of said recording medium.

7. An information recording apparatus according to claim 6 , wherein a thickness of said soft magnetic film is adjusted so that a magnetic field generated between said pair of magnetic poles is not less than a coercive force of said recording medium at said adjacent point or said contact point to said soft magnetic film of said surface of said recording medium.